“Thin client” technologies are commonly used to prevent information leaks and to reduce operation and maintenance costs of personal computers (PCs). In a thin client system, clients have minimum functions and a server manages resources such as applications and files.
In such a thin client system, although the server actually executes processes and causes the clients to display the results of the processes and data stored in the server, it appears as if the clients themselves execute the processes and store the data.
For example, in a thin client system, a server executes business applications such as a word processor and a mailer, and causes clients to display the processing results of the business applications. Here, it is desired to use a wider range of applications in a thin client system in addition to business applications as described above. Examples of such applications include an application (e.g., a computer-aided design (CAD) application) for processing detailed images and an application for processing videos.
However, when large-volume data such as images and videos are transmitted via a protocol such as a Remote Desktop Protocol (RDP) or a Remote Frame Buffer (RFB) protocol for Virtual Network Computing (VNC) used for communications in a thin client system, the response time of operations performed at clients increases. This problem occurs not only in processes involving transmission of images and videos, but in any process involving transmission of high-volume data for screen updates between a client and a server in a thin client system.
Japanese Laid-Open Patent Publication No. 2010-282609 discloses a technology for reducing the amount of data transmitted. In the disclosed technology, either updated display data itself or data primitives that implement the updated display data are transmitted based on transmission efficiency.
Japanese Laid-Open Patent Publication No. 2007-265220 discloses a technology where identifiers and area information of images are transmitted to a display device when those images are stored in the display device.